Drafting instrument.



PATBNTED JULY 30, 1907.

L. M. SHERIDAN. DRAFTING' INSTRUMENT..

APPLICATION FILED SEPT. 24,1906.

W JTNESSES: W

A TTORNE Y5 LESLIE M. SHERIDAN, OF- ANAGONDA, MONTANA,

' DRAFTING INSTRUMENT.

Specification of Letters Patent.

Patented July so, 1907.

Application filed September 24,1906. Serial No. 335.930.

To all whom it may rom'cr'n:

Be it known that I, Lustre M. SHERIDAN, a citizen of the United States,residing at Anaconda, in the county of Deerlodge and State of Montana,have \invented a new and useful Drafting Instrument, of which thefollowing is a specification.

This invention relates to an instrument designed to be used bydraftsmen, engineers, and thelike, to take the place of templets, knownto the trade as railroadcurvcs, for drawing geometrical curvesapproximating spirals, ellipses and arcs of circles of any radii fromzero to infinity, and where the centers are unknown.

The principle on which the instrument operates is based upon the factthat when the legs of a fixed or constant angle are guided by twostationary points, the vertex of the angle will describe an arc of acircle, while a point lying in a line bisecting the angle will describea portion of an ellipse, and a point along either of the legs willdescribe a portion of a spiral.

The invention has for one of its objects to provide a curve drawinginstrument of the character described which is of simple and improvedconstruction arid by which a large variety of curves can be convenientlydrawn.

A further object of the invention is the provision of an instrument ofthe nature referred to, which is so constructed that it is readilyadapted for use as a protractor, a triangle whose angles are adjustable,and as a device for drawing straig' t, as well as curved, lines.

With these objects in view, and others, as will appear as the nature ofthe invention is better understood, the invention comprises the variousnovel features of construction and arrangement of parts, which will bemore fully described hereinafter and set forth with particularity in theclaims app ended hereto.

In the accompanying drawing, which illustrates one embodiment of theinvention, the full lines show the instrument in plan while the dottedlines show the movable parts of the instrument in two positions toindicate the describing of a curve.

Referring to the drawing, 1 and 2 designate the legs of the instrumentwhich are preferably made of strip metal, such as brass, German silver,aluminium, or the like, and carefully finished to form straight edges sothat the legs may be used as a triangle for drawing straight lines. Eachleg is provided witha longitudinal slot 3 extending substantially theentire length thereof and the adjacent ends of the legs are hingedtogether by an annular rivet 4. At the open side of the angle formed bythe two legs is a beam or member 5 that carries the guiding points forguiding the movement of the legs 1 and 2. The member 5 is also a stripof suitable material having straight edges and one or both of theguiding pins or points may be adjustably mounted thereon. In the presentinstance, the left hand guiding pin is in the nature of a screw 6engaging in a threaded aperture of the lug 7 formed on the member 5. Theshank of the screw extends through the slot 3 of the leg 1 and permitsthe leg to move freely along the same.

11 formed on the slide, thereby insuring the permanent engagement of thepin 8 with the slot of the leg 2.

On one of the legs, as, for instance, the leg 1, is a segmental arm 11preferably formed integral therewith and extending over the leg 2. Thisarm is provided with scales in the denomination of degrees and inches,so that the instrument may be used as a protractor, when desired. Theleg 2 is provided with a clamping screw 12 that clamps the arm 11 andleg 2 together so that the said arm forms a convenient means for firmlyholding the legs 1 and 2 in fixed angular adjustment.

Arranged over the segmental arm 11 is acentral arm 13 which is providedwith a longitudinal slot 14,and is pivoted at one end to the legs 1 and2 by the rivet 4. This arm is preferably made of strip material similarto the legs of the instrument and is arranged to be clamped in fixedposition with respect to the segmental arm '11 by a clamping screw 15and nut 16.

With an instrument constructed as above described, an arc of a circlecan be drawn by placing a pencil at the vertex of the angle formed onthe legs 1 and2,

preferably in the annular rivet 4. The member 5 is held stationary onthe drawing board by one hand while with the other hand, which holds thepencil at the vertex of the angle, the legs are moved around on theguiding pins 6 and 8, so that a curve, such as a and b is produced. Thedotted line positions show the legs being moved to the left from thecentral or full line position, and it will be obvious that, by movingthe legs to the right, an arc corresponding to a and b will bedescribed, making thereby an approximate semi-circle. By placing thescriber or pencil at any point along the slot 14 of the central arm 13,a curve, such as c, (I, will be generated, while a curve, such as e, f,will be produced by placing the pencil along either of the legs. Thepencil is held in one hand of the operator with the point portionthereof extending through the slot of any member 1, 2 or 13 and bearingagainst the wall of the slot to steady the pencil. In thismanner,

the pencil can be held in proper position as the device ol these guidingpoints resnlts in a corresponding ehange in the effective radius ofmovement.

I have described the principle of operation of the invention, togetherwith the apparatus which I now consider to be the best embodimentthereof, but I desire to have it understood that the apparatus shown ismerely illustrative, and that various changes may be made, when desired,as are within the scope of the invention.

What is claimed is 1. In a device of the class described, thecombination of two longitudinally slotted legs, a pivot connecting thecorresponding ends of the legs. means adjustably connecting the legs tohold them in fixed angular relation, ameniber adapted to he heldstationary and arranged with its extremities overlapping the legs, ailxed guiding pin on the said member loosely extending into the slot ofone of the legs, a slide on the member, means for holding the slidestationary, and a pin on the slide movably engaging in the slot of theother leg.

2. In a device of the class described, the comhinationot twolongitudinally slotted legs, a pivot connecting the slotted v n rmcorre'spi mdipg ends of the legs, a segmental arm on one of the legs, aclamping device on the other leg engaging the said arm for holding thelegs in fixed angular relation, 11 member adapted to be held stationaryand extending from one leg'to the other, and guiding pins on the saidmember engaging in the slots of the legs.'

3. in a device of the class described, the combination of tweiongitudinallyslotted legs, a slotted arm, a rivet pivotally connectingthe legs and arms together, a segmental arm on one '01 the legs, afastening device on the other leg cooperating with the segmental arm foradjustably holding the legs in angular relation, a fastening device onthe eoiiperating with the segmental arm to hold the iirst arm in iixodposition, a member adapted to be held stationary and extending from oneleg to the other, and guiding pins mounted on the said member to beadjustable and engaging in the slots of the legs for guiding themovement otth'e latter.

In testimony. that I claim the foregoing as my own," I have heretoaflixed mysigna'ture in the presence of two.

witnesses.

' LESLIE M. SHERIDAN. Witnesses: j

It. R. Ivns, \VM. E. MCCLELLAND.

